There are many reasons why a book might be unavailable.
Sometimes a book goes temporarily out of print - and sometimes no audio version has ever been recorded. Audible wants to give you the most complete selection we can and we'll keep adding series and filling in gaps as quickly as possible.
Have not read the print version.
I have enjoyed all of 'The Arcadian' books, this one was a bit out there short story, great narration as usual Sean is a master storyteller.